Hydrocarbons are valuable commercial products. For example, ethylene, propylene, benzene, toluene, and para-xylene are valuable commercial products useful in the production of polymers, gasoline, and other chemicals.
Olefins and aromatic compounds can be formed by catalytic and separation processes. For example, aromatic compounds can be formed by converting non-aromatic compounds to aromatic compounds, e.g., dehydrocyclo-oligomerization, reforming, and catalytic cracking. Also, less valuable aromatic compounds can be converted into more valuable aromatic compounds. Examples of such processes include the methylation of toluene to form xylenes, the disproportionation of toluene to form xylenes and benzene, and the isomerization of xylene feedstock to produce a product enriched in para-xylene. Olefins can be produced by catalytic cracking of paraffins, e.g., a fluidized catalytic cracking process. High value purified olefins and aromatics can be manufactured by separation processes such as selective adsorption processes. Examples of such processes include Parex™, which separates para-xylene from mixed C8 aromatic isomers, Olex™, which separates olefins from paraffins in a wide boiling hydrocarbon mixture, and Ebex™, which separates ethylbenzene from mixed C8 aromatic isomers. These processes typically use at least one solid particulate material, such as a catalyst and/or a solid adsorbent.
Many commercial catalytic and adsorption processes suffer problems such as, deactivation, coking, and overall attrition resulting in high pressure-drop across a catalyst bed or adsorbent bed. These problems can degrade or otherwise impair the performance of the process such as conversion, selectivity, and productivity (including overall product recovery). In some instances these problems can require alteration of operation conditions of the process such as temperature, pressure, and weight hour space velocity (WHSV). One solution to the problems for catalytic processes is to compensate for activity lost due to the catalyst deactivation by increasing reaction temperature. However, increasing the reaction temperature increases energy consumption. Furthermore, the reaction temperature is limited by the metallurgy of the reactor material. Another solution to these problems for catalytic and/or adsorption processes is regeneration or rejuvenation of the catalyst or adsorbent, which normally requires unit shut down for a certain period of time. In some cases, fresh catalyst or adsorbent will have to be reloaded to replace the spent catalyst or adsorbent.
Typical reactors and adsorption chambers have a designed pressure-drop depending on the applications. The pressure-drop across the catalyst bed or the adsorbent bed typically increases over time after the catalyst bed or the adsorbent bed is brought on-line. Extra pressure-drop across the catalyst bed or the adsorbent bed is an operational problem in commercial hydrocarbon conversion processes. While not intending to be limited to any theory, we believe that the extra pressure-drop across the catalyst bed or the adsorbent bed results from the formation of fines (including attrition and/or crushing of adsorbent and/or catalyst), coke formation, deposition of impurities and/or solids in the feedstock(s) on the catalyst or adsorbent, and movement of the catalyst or adsorbent in the reactor or the adsorption vessel. One solution to this problem is to increase pressure head for the feedstream(s), but increasing the pressure head increases energy consumption. Furthermore, the maximum pressure head is limited by the mechanical design of associated equipment and the process conditions of the upstream and/or the downstream processes. In some cases, the catalyst and/or adsorbent have to be changed-out with fresh or regenerated catalyst and/or adsorbent, which requires a costly unit shutdown.
U.S. Pat. No. 3,838,038 (Greenwood et al.) and U.S. Pat. No. 3,838,039 (Vesley et al.) disclose a process for hydrocarbon processing in conjunction with continuous catalyst regeneration. The process utilizes a moving bed reaction zone and a continuous regeneration zone, which causes the burning of carbonaceous material off of a catalyst that has been withdrawn from the reaction zone. The regenerated catalyst is continuously supplied back to the moving bed reaction zone.
U.S. Pat. No. 5,589,057 (Trimble et al.), U.S. Pat. No. 5,599,440 (Stangeland et al.), U.S. Pat. No. 5,603,904 (Bachtel et al.), and U.S. Pat. No. 5,076,908 (Stangeland et al.) disclose a reactor having a cone or screen at the bottom thereof to support the catalyst. The catalyst stream enters at the top of the reaction counter-current to the flow of the gas and the hydrocarbon, which enters at the bottom. As the feed moves up through the catalyst, these particles become heavier and move downward through the reactor toward the entering feed stream and are finally withdrawn at the bottom of the reactor.
U.S. Pat. No. 2,921,014 (Marshall), U.S. Pat. No. 3,161,582 (Wickham), U.S. Pat. No. 3,424,672 (Mitchell), U.S. Pat. No. 3,448,037 (Bunn, Jr. et al.), and U.S. Pat. No. 5,310,477 (Lomas) disclose catalytic cracking of hydrocarbon feed in a fluidized bed with smooth and stable catalyst circulation and regeneration. The spent catalyst is constantly removed from the reaction zone, regenerated in the regenerator and resupplied back to the reaction zone.
The present invention relates to a hydrocarbon conversion process comprising a step of removing, under the conversion conditions without interruption of on-going process, at least a portion of the solid particulate material in the reaction and/or separation zone.